1. Field of the Invention
The present invention relates to a paper feeding apparatus which has a skew reducing function of recording paper or the original used in a printing or reading apparatus.
2. Description of the Related Art
In feeding the original to be read with sensors or in feeding recording paper to be printed, since the technique to reduce skew of paper is extremely important for carrying out precise printing, currently, a variety of techniques have been proposed.
For example, in Japanese Unexamined Patent Publications JP-A 59-64450 (1984) and JP-A 61-263552 (1986), a technique to prevent a jam from occurring is disclosed, in which skew of a fed paper is detected by means of optics.
In Japanese Unexamined Patent Publications JP-A 61-229755 (1986) and JP-A 62-285829 (1987), a technique to prevent skew of paper is disclosed in which the fed paper is made to come in contact with the shutter or a roller.
In Japanese Unexamined Patent Publication JP-A 10-87108 (1998), a technique to prevent skew by making the paper come in contact with a roller or the like is disclosed, in which a concrete setting method to feed paper successively is proposed.
In Japanese Unexamined Patent Publication JP-A 63-272736 (1988), a technique used in an both-sides reading apparatus is disclosed, in which a butting portion member is commonly used for reading one side of an original and for reading another side of the inversed original.
In Japanese Unexamined Patent Publication JP-A 5-58012 (1993), a technique is disclosed, in which a pair of two sensors disposed in the direction of transport direction of the paper are made to move in a direction orthogonal to the transport direction of the paper, and each output pattern is interpreted logically to determine transportation status of the paper.
In Japanese Unexamined Patent Publication JP-A 11-322131 (199), a technique to prevent skew from occurring is disclosed, in which a skew of a manually fed paper is detected, means for transporting paper not only in the forward feed direction but also in the backward direction is provided, a paper having a skew exceeding a predetermined amount is transported in the backward direction and discharged.
As described hereinbefore, it is a critical problem for carrying out a precise printing how to reduce skew of paper being fed, or what countermeasures should be taken after detecting a skew.
In these cases, the above-described countermeasures are too complex in structure or too expensive, and accordingly disadvantageous to a simple-structured paper feeding apparatus.
Herein, the simplest preventive method of skew is to provide paper guides as long as possible to the paper hopper on which paper is placed along the paper feed direction to regulate the position of the paper by means of the paper guide.
However, in order to detect of the status of the paper placed on the paper hopper, it is necessary to detect the paper by providing a paper sensor or a paper size sensor to the paper hopper.
Further, in case where too long paper guide is provided, since these sensors prevent the paper guide from moving when the guide is moved on the paper hopper, the length of the paper guide is restricted by the position of these sensors.
The invention was made to provide a paper feeding apparatus having a simple structure that reduces skew of paper reliably and enables a precise printing by virtue of paper feed guides that is not restricted by the position of the sensors.
The invention provides a paper feeding apparatus comprising a loading table having a loading plane on which paper is placed, a paper guide disposed to be movable in a second direction orthogonal to a first direction in which the paper is fed so as to come in contact with a side face of the paper at the second direction side to regulate a position of the paper, and a sensor provided with an actuator disposed to be movable in a direction of a normal to the loading plane, for detecting status of the paper on the loading table based on a position of the actuator in the direction of the normal to the loading plane, wherein the actuator is retracted in the direction separating away from the loading table along the direction of the normal to the loading table by a contact of the actuator with the paper guide movable in the second direction.
According to the invention, in the case where the paper guide is moved to regulate the paper, even when the actuator is disposed within the working area of the paper guide, since the actuator retracts out of the working area of the paper guide by virtue of an external force given by the paper guide, the actuator does not prevent the paper guide from being moved. By virtue of this, the length of the paper guide is not restricted by the position where the sensor is disposed. As a result, it is made possible to regulate the position of the paper more precisely as much as the length of the paper guide is made longer result in reliable prevention of skew on the paper by means of a simple structure.
In the invention it is preferable that the paper guide is movable in accordance with the size of the paper between the actuator separated away from the loading table and the loading table.
According to the invention, the paper guide is adapted to pass through the point where the actuator is disposed. Accordingly, since it is made possible to move the paper guide on the paper-loading table in accordance with the size of the paper to regulate the position of the paper, skew of the paper is reliably prevented.
In the invention it is preferable that the actuator has a shaft extending along an axis parallel to the normal to the loading plane and a sliding portion formed on one end of the shaft in a longitudinal direction close to the loading plane and extending in the second direction, for sliding on the paper guide, the sliding portion is formed so that a distance between the sliding face and the axis of the shaft is enlarged from the one end of the shaft in the longitudinal direction toward the another end in the longitudinal direction.
According to the invention, by virtue of the configuration of the actuator of which sliding portion is basically extending toward the another end of the shaft, when an external force is given by the paper guide, the external force acts on the actuator so that the actuator is lifted up in the direction separating away from the loading table along the normal to the loading table. Accordingly, it is made possible to make the actuator retract using the moving force of the paper guide.
The Same as the above, by means of movement of the paper that moves in the paper feed direction, the actuator moves to the upper face of the paper. Accordingly, it is made possible to detect the amount of the paper.
Therefore, since it is not necessary to provide a driving apparatus or the like for the aforementioned operation, it is made possible to give the paper feeding apparatus a simple structure.
In the invention it is preferable that the sliding section is disposed at both sides of the shaft in the second direction.
According to the invention, since the sliding section is disposed at both sides of the shaft of the actuator, even when the paper guide comes in contact with the actuator from either side in the second direction, the actuator is made to retract and the paper guide passes through under the retracted actuator. By virtue of this, it is made possible for the paper guide to pass through under the actuator in either direction.
Therefore, it is made possible to move the paper guide in accordance with the size of the paper to regulate the position of the paper.
In the invention it is preferable that the paper guide has a notch which is formed at a portion where the paper guide comes in contact with the actuator.
According to the invention, in the portion where the paper guide comes in contact with the actuator, since the notch is formed on the paper guide so as to be, comparing to the other portions, lower, it is made possible to make the distance of retraction of the actuator to be small. Whereas, since the other portions excluding the notch have enough height to regulate the position of the paper, the notch does not have any problem to regulate the position of the paper. Accordingly, it is made possible to regulate the position of the paper precisely.
In the invention it is preferable that the loading table is provided with a concave portion to which the actuator fits.
According to the invention, since the paper is detected at a position closer to the loading table as much as the actuator engages with a concave portion, it is made possible to make the paper detecting function to be executed without depending on the amount of the paper.
Therefore, the invention provides a paper-feeding apparatus that enables to reliably reduce skew on the paper resulting in a precise printing by means of a simple structure.